1. Field of the Invention
The present invention relates to D.C brushless motor, and more particularly to D.C brushless motor each having a balance plate for assuring stable rotational movement of the rotor axle, wherein the balance plate can be fixed easily and wherein the balance plate has a gap to a metal axle tube and to an adjacent pole plate of the stator so that the balance plate is not magnetized when the stator is energized.
2. Description of the Related Art
U.S. Pat. No. 6,050,785 to Horng issued on Apr. 18, 2000 discloses D.C brushless motor each comprising a housing, a circuit board, a balance plate, a stator, a rotor, and a cover plate. The balance plate and a permanent magnet on the rotor attract each other to assure stable rotational movements of the rotor relative to the stator. Nevertheless, it was found that manufacture of such D.C brushless motor is troublesome and inconvenient when considering fixing of the balance plate and preventing magnetic inductivity between the polar plate and the balance plates of the stator and the axle tube.
It is an object of the present invention to provide an improved D.C brushless motor that includes a balance plate which can be positioned or fixed easily and which has no magnetic inductivity with the pole plates of the stator and the axle tube.
In accordance with the present invention, a D.C brushless motor includes a housing, a circuit board, a balance plate, a stator, a rotor, and a magnetically non-inductive member. The housing includes a compartment, and a bottom wall that defines the compartment. A tube seat formed thereon for engaging with an axle tube of the stator. The central hole of axle tube receives a rotational shaft of the rotor. The rotor includes a permanent magnet mounted to an inner periphery thereof. The balance plate includes a fixing hole so as to be mounted around the axle tube of the stator, wherein there is a gap between an inner periphery defining the fixing hole and the axle tube. The balance plate is made of magnetically inductive material such that the balance plate and the permanent magnet attract each other. The magnetically non-inductive member avoids contact between the pole plate of the stator and the balance plate. In addition, the magnetically non-inductive member may include a flange inserted into the gap between the inner periphery of the fixing hole of the balance plate and the axle tube.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.